This invention relates generally to tote containers which are constructed from a blank of sheet material and the blanks used to form those tote containers, and particularly to a corrugated plastic tote container blank having a diagonally biased grain.
Tote containers which may be cut, scored, and folded to form an upright receptacle from a blank of corrugated paperboard, fiberboard, or plastic are well known to the art. The configurations of those containers, and the respective blanks, range from simple rectangular sheets to complex geometric structures.
Current improvements in tote containers generally relate to a distinct function or use for the tote container, or a particular modification which makes the tote container uniquely superior or more suitable for a particular purpose. These improvements and modifications may relate to any number of features of the tote container, such as the size, shape and manner of interconnecting the panels, the lid, locking structures, stacking capabilities, materials, capacity, durability, and so forth.
Of particular concern to this invention are those tote containers fashioned from a blank which is cut and scored from a three-ply corrugated plastic sheet material. This corrugated plastic sheet material has two planar plies spaced a short distance apart, and a corrugated intermediate ply or series of beams connecting those planar plies. The manufacturing methods for a corrugated plastic sheet material of this type are discussed in U.S. Pat. Nos. 4,267,223; 4,188,253; and 4,132,581.
In general, the plies are extruded and processed through a corrugating machine which bonds them together into a linear corrugated sheet structure which may be rolled or cut into sections. The corrugated sheet has a grain defined by the convolutions of the intermediate corrugated ply.
The corrugated plastic sheet material is then processed in roll or section form to produce the blanks. The sheet material is transported through various feed rollers and dyes which are used to cut out the overall shape of the blank; and scoring rollers are used to impress a pattern of score lines into the surface of the blanks corresponding to the position of the fold lines and panel edges. The waste material outside the perimeter of the blank, and that resulting from material which is removed to form handgrips, ventilation holes, and the like, is discarded or recycled. The blanks may be divided into separate units at this time, or remain as a series of interconnected sections.
The overall external shape of the blank traditionally conforms to a generally square or rectangular form which aids in conserving material, although many alternative shapes such as arcuate or octagonal are known. Examples of square and rectangular blanks are disclosed in U.S. Pat. Nos. 4,600,142 and 4,572,425. An arcuate configuration is shown in U.S. Pat. No. 3,982,690. The exact definitions that the shape of a blank may take, and the general overall shapes of blanks, are effectively limitless.
In positioning the outline of the blank and orienting the score lines on the sheet of corrugated material, the grain is ordinarily aligned so as to extend either parallel with or perpendicular to the edges of the bottom panel or side panels, such that the corrugations lie either parallel or perpendicular to the major or minor axis of the tote container. In this manner, the corrugations will often traverse the bottom panel and extend upwardly along at least two of the side panels to provide for continuous vertical and underlying support.
It is thus incumbent upon the designers of tote containers, and particularly those manufactured from corrugated plastic sheet material, to attempt to incorporate certain universal and well recognized advantages into these tote containers.
One such common advantage is to reduce the amount of material consumed in fabricating the blank, either the material that is used to construct a tote container with a receptacle having a predetermined volume and shape, or the amount of material that is discarded or recycled after the blank is formed.
Another common advantage is to increase the overall strength, durability, and load bearing capacity for a particular design of tote container, through better materials, bonding or fastening means, or placement and orientation of the panels, joints, seams, folds, closures, and other structural features. Another method for achieving this advantage has been to place handgrip openings along the end panels of the tote container, which are then connected by a rim member, with the primary weight supporting side panels being attached to the central portion of the rim member such that the parallel grain of the corrugations extends under the receptacle to form a support along the longitudinal length of the container.
A related advantage is to increase the ease of scoring and folding the tote container, thereby making the tote container simpler and less expensive to assemble, and in turn increasing the strength and structural integrity of the joints, folds, and seams.
Another desired advantage is to increase the number of vertical panels, or the interconnections between those panels, so as to distribute the weight of the load placed in the receptacle over the largest area of vertical support possible.
In attempting to achieve these advantages, however, numerous problems unique to the corrugated plastic sheet material, and therefore not occurring to the same degree in tote containers constructed of paperboard or fiberboard, must be confronted. Far greater pressure is required to score a three-ply corrugated plastic than fiberboard or paperboard, and the scoring rollers and dyes must be carefully aligned along the corrugations. The dimensional tolerances and position of the tote container blank must be strictly controlled in order to prevent perforations of the planar plies and crushing of the intermediate ply, and the dimensional specifications of the tote container then become dependent upon the given corrugated plastic material rather than being dictated by the optimum design configuration for the particular function and construction of that tote container.
Poorly aligned and positioned cut or score lines will also cause splitting and fraying of the free end edges of the tote container. If the tote container is of a type which is repeatedly folded and unfolded, or has some particular mechanical movement of the panels, lid, or closure associated with using the container, these and other similar defects can prevent the tote container from functioning properly or conveniently. The blank must therefore be processed through the cutting and scoring rollers or dyes with great precision.
It is a related advantage to obtain crisp and uniformly scored creases, seams, and folds, which will not roll or shift due to the grain of the corrugated plastic, and to accordingly eliminate the dependency between the dimensional specifications and tolerances of the tote container and the placement of the grain of the corrugated plastic.